From: Sebastian Hungerecker <sepp2k@...>
Date: 2007-09-02T02:53:01+09:00
Subject: Re: gsub ?

Josselin wrote:
> I don't manage very well the gsub function, not too bad with simple
> one, but when it comes to string containing slashes, I totally mess it..

Use %r{your_regex} instead of /your_regex/ - then you don't have to escape the
slashes.

> my string can be srt = "/cities/31550/posts;search"
>
> and I would like
> 1-   detect that srt is a string of this type      /cities/  nnnnn
> /posts;search"   where nnnnn is a number between 1 and 99999

%r{/cities/(\d{1,5})/posts;search}
\d{1,5} is "one to five digits" and the parens tell it to remember that as 
group 1.

> 2- if srt is of this type, then replace the number nnnnn by another one 
> ppppp

srt.sub(%r{/cities/(\d{1,5})/posts;search}) do
  new_number=$1.to_i * 2 # (Or however the new number is calculated)
  "/cities/#{new_number}/posts;search"
end
If the new number is fixed (i.e. it doesn't depend on the old number), you can 
just do:
srt[%r{/cities/(\d{1,5})/posts;search},1]="102943"

> btw : what's the best link to learn more abour gsub... ?

There's not much to gsub itself. It's just string.gsub(re,str) or 
string.gsub(re) {|match| do_something; return a string}
What you want to learn more about are regular expressions.
You can do that at at www.regular-expressions.info


HTH,
Sebastian
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